Authors: By ALESSANDRA RIZZO
PERUGIA, Italy (AP) -- Questions mounted Tuesday over crucial DNA evidence linking Amanda Knox and her co-defendant to the murder of her British roommate, with forensic experts giving detailed and conflicting views in court over genetic science.
Knox felt "disoriented" after two days listening to the reports about DNA extraction and attribution, her lawyer said. A prosecution consultant and a lawyer suggested further testing on DNA evidence might be warranted, a step prosecutors might decide to push for as the appeals trial continues.
Without a clear motive or convincing witnesses, much of the appeals outcome hinges on how the court views the DNA evidence.
"In the morning it goes one way, in the afternoon another. It's two schools of thoughts facing off on scientific theories," said Luciano Ghirga, a lawyer for Knox. "The issue becomes more and more important every day."
Knox and Raffaele Sollecito were convicted of sexually assaulting and killing Meredith Kercher in November 2007 in the apartment Knox and the 21-year-old Briton shared while studying in Perugia. Knox was sentenced to 26 years in prison; Sollecito to 25. Both deny wrongdoing and have appealed the December 2009 verdict.
In the original trial, prosecutors maintained that Knox's DNA was found on the handle of a kitchen knife believed to be the murder weapon, and that Kercher's DNA was found on the blade. They said Sollecito's DNA was on the clasp of Kercher's bra as part of a mixed trace that also included the victim's genetic profile.
But a review of the DNA evidence ordered by the appeals court disputed those finding and criticized the forensic police who carried out the original investigation for shoddy work - setting off the current battle.
The court-appointed experts alleged glaring errors in evidence gathering, below-standard testing which they said raised doubts about the attribution of DNA traces, and possible contamination of the evidence.
Patrizia Stefanoni, the police expert who examined DNA traces in the aftermath of the 2007 killing, defended her job in testimony spread over two days and with the aid of over 100 slides. She rejected claims that she had tested and extracted profiles from insufficient or unreadable traces of DNA.
Stefanoni said the knife, found at Sollecito's house, was tested in a lab six days after the investigators had analyzed a trace of Kercher's DNA - excluding contamination.
The bra clasp, however, was recovered off the floor at the crime scene 46 days after the killing. The independent review said that the "context ... was highly suggestive of ambient contamination."
Stefanoni insisted that in that period "nothing from outside the victim's room was brought inside." She insisted that out of 133 specimens analyzed in the house of the murder - including 89 in Kercher's room - Sollecito's genetic profile was only found in a cigarette butt in an ashtray, mixed with Knox's.
"If Sollecito's DNA had somehow traveled from the butt to the clasp, then there would be Knox's DNA as well on the clasp," she said Tuesday.
Enter defense consultant Adriano Tagliabracci, who said he could rule out that Sollecito's DNA was in fact on the clasp.
"It is 29,000 times more likely that another individual left that (genetic) material on that clasp than Sollecito," he said.
Tagliabracci, brought in by Sollecito's defense, also noted that the clasp, when collected, was a few feet (meters) away from where it had originally been seen in a crime scene police video.
"It was moved by somebody, we don't know how, and it's possible that it was turned upside down," Tagliabracci told the court. "How can we be certain that that is a reliable exhibit?"
Stefanoni, the police expert, maintained the clasp was always facing upward, meaning it had not been contaminated by touching the floor.
The detailed explanations of DNA analysis techniques, equipment and theory - often performed with slides in a dimly-lit, hot courtroom - sorely tested the attention spans of many in the frescoed room. Knox herself appeared to nod off for a second Tuesday, her eyes apparently closed and her head falling forward at one point.
Presiding Judge Claudio Pratillo Hellmann more than once asked the experts to be succinct and clear in their answers. At one point, he even joked.
"I'm glad to see you have no slides," he said with a wry smile as a geneticist was taking the stand - only to have his hope dashed.
One of the court-appointed experts, Carla Vecchiotti, said the trace on the bra clasp was so mixed that a very high number of genetic profiles could be extracted - her own or that of the presiding judge for that matter.
Prosecution consultant Giuseppe Novelli struck back at the independent experts, saying they could have and should have retested the material still present on the blade, as their mandate allowed them to do.
The same point was made by the police officer, Stefanoni, who said that new DNA kits could successfully read that amount, however low. The experts decided not to attempt a retest, saying the material was insufficient, and limited themselves to assessing procedures carried out in the original investigation.
The prosecutors might choose to press for such a retest Wednesday, when Knox's genetic consultants will be heard. Francesco Maresca, lawyer for the Kerchers, contended the independent review was "incomplete and superficial," also suggesting further testing.
A verdict is expected by the end of September.